1. Field of the Invention
The present invention relates to a method of producing an electrophotographic photosensitive member comprising a functional film.
2. Description of the Related Art
As a substrate for forming a deposited film of an electrophotographic photosensitive member, glass, heat-resistant synthetic resins, stainless steel, aluminum, and the like have been proposed. However, in order to perform an electrophotographic process comprising charging, exposure, development, transfer, and cleaning, and to keep positional precision at a constant, high level to maintain high image quality, a metal is frequently used for practical applications. Particularly, aluminum has good workability, is inexpensive and lightweight, and is thus an optimum material as a substrate for the electrophotographic photosensitive member.
Techniques for forming substrate materials for the electrophotographic photosensitive member are disclosed in Japanese Patent Laid-Open Nos. 59-193463 and 60-262936.
Japanese Patent Laid-Open No. 59-193463 discloses a technique in which a supporting member comprises an aluminum alloy containing 2000 ppm or less of iron (Fe) to obtain an electrophotographic photosensitive member comprising amorphous silicon which is capable of forming images with good quality. This publication also discloses a procedure comprising cutting a cylindrical substrate by a lathe to a mirror surface, and then forming amorphous silicon by glow discharge.
Japanese Patent Laid-Open No. 60-262936 discloses an extruded aluminum alloy having the excellent property of vapor deposited amorphous silicon and comprising 3.0 to 6.0 at % magnesium (Mg), impurities composed of manganese (Mn) suppressed to 0.3 wt % or less, chromium (Cr) suppressed to less than 0.01 wt %, Fe suppressed to 0.15 wt % or less, and silicon suppressed to less than 0.12 wt %, and the balance comprising Al.
The substrates comprising these materials are subjected to surface processing to form a light receiving layer on the surfaces thereof according to application of the electrophotographic photosensitive member. Techniques for surface processing these substrates are disclosed in Japanese Patent Laid-Open Nos. 61-231561 and 62-95545. As a technique for preventing corrosion in a water washing step when an aluminum alloy is used as the substrate, Japanese Patent Laid-Open No. 6-273955 discloses a technique in which a substrate is washed with water containing dissolved carbon dioxide. However, this publication does not disclose that the film thickness and the composition ratio are defined in predetermined ranges by using water containing a specified inhibitor.
Japanese Patent Laid-Open Nos. 63-311261 and 1-156758 and Japanese Patent Publication No. 7-34123 disclose techniques for forming an oxide film on an Al substrate, but do not disclose that a film is formed after washing with water containing an inhibitor containing specified components.
Japanese Patent Laid-Open No. 3-205824 discloses the technique of washing by injecting high pressure, but discloses neither washing by using a ring comprising nozzles set to specified conditions, nor washing with water containing a specified inhibitor. Japanese Patent Laid-Open No. 8-44090 discloses that an electrophotographic photosensitive member is formed by using a substrate subjected to surface treatment with a silicate solution, but discloses neither washing by using a ring comprising nozzles set to specified conditions, nor washing with water containing a specified inhibitor.
As materials used for the electrophotographic photosensitive member, various materials have been proposed, which include selenium, cadmium sulfide, zinc oxide, amorphous silicon, organic materials such as phthalocyanine, and the like. Particularly, a non-single crystal deposited film containing a silicon atom as a main component represented by an amorphous silicon film, for example, an amorphous deposited film composed of amorphous silicon which is compensated by hydrogen and/or halogen (e.g., fluorine, chlorine, or the like), has been proposed for a pollution-free photosensitive member having high performance and high durability; some of such materials have been put into practical use. Japanese Patent Laid-Open No. 54-86341 discloses a technique for an electrophotographic photosensitive member comprising a photoconductive layer mainly made of amorphous silicon.
Conventional methods of forming such a non-single crystal deposited film containing a silicon atom as a main component include a sputtering method, a method (thermal CVD method) of thermally decomposing raw material gases, a method (optical CVD method) of optically decomposing raw material gases, a method (plasma CVD method) of decomposing raw material gases by a plasma, and the like.
The plasma CVD method, i.e., the method of decomposing raw material gases by radio frequency or microwave glow discharge to form a deposited thin film on a substrate, is optimum as the method of forming an electrophotographic amorphous silicon deposited film, and practical use thereof is in progress at present. Particularly, the plasma CVD method comprising decomposition by microwave glow discharge, i.e., the microwave plasma CVD method, has recently attracted attention as the method of forming a deposited film in the industrial field.
The microwave plasma CVD method has the advantages that go the deposition rate and efficiency of utilization of raw material gases are higher than the other methods. U.S. Pat. No. 4,504,518 discloses an example of microwave plasma CVD techniques taking advantage of this method. The technique disclosed in this U.S. patent comprises forming a deposited film having high quality at a high deposition rate by the microwave plasma CVD method under low pressure of 0.1 Torr or less.
Furthermore, Japanese Patent Laid-Open No. 60-186849 discloses a technique for improving the efficiency of utilization of raw material gases in the microwave plasma CVD method. The technique disclosed in this publication comprises arranging a substrate so as to surround a means for introducing microwave energy to form an inner chamber (i.e., a discharge space), thereby significantly improving the efficiency of utilization of raw material gases.
Japanese Patent Laid-Open No. 61-283116 discloses a modified microwave technique for producing a semiconductor member. Namely, this publication discloses a technique in which an electrode (a bias electrode) for controlling plasma potential is provided in a discharge space so that in film deposition, a desired voltage (a bias voltage) is applied to the bias electrode to control ion attack on the deposited film, thereby improving the characteristics of the deposited film.
Specifically, when an aluminum alloy cylinder is used as the substrate, the method of producing an electrophotographic photosensitive member by the above-described techniques is carried out as follows.
The aluminum alloy cylinder is processed to flatness in the predetermined range by diamond tool cutting using a lathe, a milling lathe, or the like according to demand, and then washed with triethane. After triethane washing, a deposited film mainly composed of amorphous silicon is formed as a deposited film of the photoconductive member on the substrate by a glow discharge decomposition method. The thus-obtained deposited film is used for producing the electrophotographic photosensitive member.
However, the electrophotographic photosensitive member produced by the above techniques has an abnormal growth portion in the deposited film, which creates a small area in which a surface charge is difficult to load. This phenomenon significantly occurs, particularly, in the case of an electrophotographic photosensitive member comprising a deposited film such as an amorphous silicon film, which is formed by the plasma CVD method. However, the area where surface potential is barely loaded can be minimized by optimizing surface processing conditions, washing conditions, and deposition conditions for the substrate. Such an area is conventionally in a level equivalent to or lower than the development resolution, and thus causes no practical problem in the electrophotographic photosensitive member.
However, recently, 1) as the development resolution has been improved with demand for improving the quality of the image formed by the electrophotographic photosensitive member, and 2) as charging conditions have been made more severe with increases in the process speed of a copying machine, it has been pointed out that the area where surface potential is barely loaded greatly affects the potential of the peripheral region thereof, resulting in an image defect.
Furthermore, since a conventional electrophotographic apparatus is mainly used for copying characters, and thus mainly used for a character original (i.e., line copy), an image defect causes no great problem in practical use. However, as the quality of the image copied by a copying machine has recently increased, a halftone original such as a photograph has frequently been copied. Therefore, there is now demand for an electrophotographic photosensitive member having less abnormal growth portions. Particularly, in a color copying machine which has recently been popularized, such an abnormal growth portion visually appears, and thus an electrophotographic photosensitive member having less abnormal growth portions is required.
Since the abnormal growth portion is small, it is difficult to detect the presence of the portion even by measuring conductivity using an electrode attached to the upper portion of the deposited film. However, when the electrophotographic photosensitive member is used in an electrophotographic process comprising charging, exposure, and development, particularly when a uniform halftone image is formed, a small potential difference on the surface of the electrophotographic photosensitive member significantly visually appears as an image defect. Particularly, in an electrophotographic photosensitive member produced by using the microwave plasma CVD method, the above-mentioned problem significantly occurs.
On the other hand, such an image defect occurs, particularly, in an electrophotographic photosensitive member produced by using the plasma CVD method, as compared with an Se electrophotographic photosensitive member produced by using vacuum deposition, and an OPC (Organic Photoconductor) electrophotographic photosensitive member produced by using a blade coating method or a dipping method.
Of devices produced by using the plasma CVD method, the above problem does not occur in a device such as a solar cell or the like, in which its performance is not affected by a small change in characteristics with the position on the substrate, and which can be modified by post processing.
Although, in conventional techniques, the substrate is washed with trichloroethane with no problem, such a chlorinated solvent should not be used due to recent environmental problems, and water washing is done instead. However, water washing of aluminum cannot be completely performed only by spraying a high-pressure washing solution, thus causing a problem in that a portion containing many impurities (Si and the like), which are partially exposed from an aluminum surface forms a local battery with a peripheral aluminum portion to accelerate corrosion of the substrate surface.